A fire broke out onboard a cargo ship leaving the International Space Station (ISS) this week, but it was no emergency. It was part of the Spacecraft Fire Experiment 2 (Saffire-II) experiment to investigate combustion in microgravity to improve safety on future spaceflights.
Nine samples were burnt in controlled conditions inside the spacecraft during the early hours of Tuesday UK time. They included silicon of various thicknesses, which is one of the most widely used flammable materials in spacecraft; a cotton-fibreglass fire retardant called Nomex; and the same acrylic glass that is used for spacecraft windows.
Data and images from all the samples have now been downloaded and the analysis is underway. The experiment follows on from Saffire-I, which took place in June. A third Saffire experiment will be conducted to build on the knowledge gleaned from this week’s run.
Fire in space is one of the least understood risks in spaceflight. The experiment took place in a Cygnus supply ship, owned by the private company Orbital ATK, which has been attached to the ISS since 23 October. It delivered 2.3 tonnes of supplies and experiments.
The Cygnus spacecraft’s mission is still not over. On Friday evening, it will deploy four shoe-box-sized satellites owned by the company Spire Global. Known as Lemur 2 CubeSats, they will track maritime traffic while collecting weather data.
Finally, on Sunday, the Cygnus spacecraft will be commanded to perform a de-orbit burn. This will cause it to burn up in the Earth’s atmosphere somewhere over the South Pacific.
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